A high-performance rocket carrying a four-frequency, phase-coherent beacon and full complement of in situ diagnostic instrumentation was launched into active equatorial spread F on July 17, 1979. In this paper we report the results of spectrally analyzing the beacon phase-scintillation and Langmuir probe data. By using simultaneous backscatter data from the Altair radar we were able to establish that the scintillation develops in high-density regions adjacent to the prominent plume structures and associated depletions. In these high-density regions the in situ spectra show a pronounced change in the power law slope near a spatial wavelength of 500 m. Larger scale structures admit a systematically varying power law index that is generally less than 2, in good agreement with a large body of Wideband satellite data and recently analyzed Atmospheric Explorer E data. Smaller-scale structures admit a spectral index much larger than 2. A single, overall power law near k -2 was found only in low-density regions that did not contribute significantly to the scintillation. The results presented here and in a companion paper suggest that refinements in the current theories of equatorial spread F near and above the F region peak are needed.

This paper announces the operational status of an auroral‐zone incoherent‐scatter radar. The Stanford Research Institute 1290‐MHz incoherent‐scatter radar, which was moved to Chatanika, Alaska (L = 5.7), an auroral‐zone location near Fairbanks, is now producing interesting new results. The siting of the radar is such that D‐, E‐, and F‐region incoherentscatter measurements can be made without ground‐clutter interference. Although coherent auroral‐clutter echoes can at times be seen at relatively low elevation angles in the north, auroral echoes are sufficiently weak at 1290 MHz in the sidelobes of the antenna that they are not detectable during normal incoherent‐scatter measurements. The capabilities of the radar system are outlined, and samples are presented of the type of incoherent‐scatter results being obtained.

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A systematic and objective approach was used to optimize the siting of the individual radars forming the Next Generation Weather Radar (NEXRAD) network. Prime consideration was given to meteorological factors, in conjunction with the user agencies' needs and the population distribution. The latter was assessed by a novel technique using weather satellite photographs showing urban illumination at night. Priority coverage areas were identified for population centers based on the expected paths of storms and their travel speeds. Radar viewing of the priority coverage areas down to low altitudes is needed so that approaching storms can be detected and warnings issued as early as possible. Other siting criteria taken into account included consideration of terrain features and local obstructions, locations of airways and civilian and military airports, electromagnetic interference, and integration of NEXRAD data into the national weather system. The methodology for selecting the network is described. Environmental impacts and costs of site acquisition and preparation were also involved in the study, but are not discussed in this paper.

An incoherent‐scatter radar facility was operated at Chatanika, Alaska (geographic and invariant latitudes both ≈ 65°N) for almost 11 years, essentially a full solar cycle. During this period, experiments lasting 24 hours and directed at nearly overhead measurements were made approximately once per month. The seasonal and solar cycle dependences of the ionosphere over Chatanika as deduced from 108 experiments spanning the 11 years are presented. The basic parameters measured were electron concentration, electron and ion temperatures, and line‐of‐sight ion velocity, all as functions of altitude and time. This paper focuses on the ionization in the E and F regions. Empirical relationships were found that enable (1) the daytime maximum E region electron concentrations to be expressed in terms of the 10.7‐cm solar flux and the solar zenith angle, and (2) the daytime maximum F region electron concentration to be expressed in terms of the 10.7‐cm solar flux alone. The dependence of nighttime precipitation‐produced ionization in both E and F regions on solar flux and magnetic activity is also described. A clear distinction between summer and winter F region ionization conditions is evident, as is the rapid switchover near the equinox.